Warming Ocean Water Melting Arctic 'Sea Ice Factories'

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The effects rising temperatures are having on the Earth's climate
are becoming increasingly apparent — and nowhere more so than in
the Arctic, where substantial sea ice melt and other signs of
warming have been observed in recent years.

Researchers now think they've figured out why climate change is
having a
more pronounced effect in the Arctic region — the influx of
water from the Atlantic Ocean that feeds into the Arctic Ocean is
warmer now than at any time in the 2,000 years prior.

Many residents of the Northern Hemisphere are suffering through
an unusually snowy and chilly winter, but while those below the
Arctic are shivering in the cold, denizens of the northernmost
latitudes have seen very warm winter months in recent years. A
climate pattern known as the Arctic Oscillation is playing a part
in this temperature flip, scientists suspect, but global warming
has also been heating up the Arctic atmosphere and oceans.

Reporting today (Jan. 27) in the journal Science, a group of
scientists from the Leibniz Institute of Marine Sciences in
Germany evaluated seafloor sediment core containing a record of
plankton dating back about 2,000 years. Based on the species
present in the sediment and a chemical evaluation of the amount
of magnesium and calcium — minerals that make up the shells of
certain organisms and fluctuate in abundance depending on water
temperature — scientists were able to determine how water
temperature has changed from around 2,000 years ago up through
the present.

The core was taken from the Fram Strait, the area where the
Atlantic Ocean feeds into the Arctic Ocean between Greenland and
the northernmost islands of Norway.

According to the researchers' analyses, throughout history, water
temperature fluctuated in the strait by only about 1 degree
Fahrenheit (0.5 degrees Celsius), even during the mini-ice age in
Europe and the relatively warmer period during the medieval ages,
until about 100 to 110 years ago, when the temperature of water
entering the Arctic began to spike.

Now, the water is about 3.6 degrees F (2 degrees C) warmer than
it was 100 years ago, or has ever been, and is likely
contributing to the
melting sea ice in Arctic waters, the study suggests.

"Many people are worried about the ice recession in the Arctic,"
Robert Spielhagen, a paleoceanographer at the Leibniz Institute
and lead author of the study, told OurAmazingPlanet.

The decrease in ice cover is usually correlated with warming
atmospheric temperatures, which do play a role, but now it also
appears that the warmer water entering from the Atlantic is
contributing as well, Spielhagen said.

In the Arctic, the
sea ice is typically about 2 to 3 meters (6.5 to 10 feet)
thick. Then there is a layer of very cold water with a lower salt
content that extends about 150 to 200 meters (500 to 650 feet)
below the surface. Below that layer is warmer, higher-salt
content water, that flows from the Atlantic through the Fram
Strait.

As the warmer water from the Fram Strait enters into the Arctic,
the heat is transferred upward, melting the ice from below,
Spielhagen explained. "Not only has the area of ice coverage been
decreasing, but also the
thickness of that ice," he said.

Even more alarming, once the water from the Fram Strait enters
the Arctic, it travels along the relatively shallow Canadian and
Alaskan continental margins, where the shelves that lead up to
the landmasses meet the deep sea. These areas are where the sea
ice is formed, so the warmer water circulating through the area
could change or even halt sea ice formation.

"It's sort of like a sea ice factory," Spielhagen said. "The
water freezes on those shelves in the winter, and then is driven
by winds into the central Arctic."

Already, the water is freezing later in the year, and the ice is
breaking up earlier. "At some point, this sea ice factory will
not work in the same way or with the same efficiency as it's been
working for hundreds of thousands of years," Spielhagen said.